Cleanup goal unlocks behaviour

core/generator/README.md

@@ -36,7 +36,7 @@ Resource class for generator balancing data.
 @export var name: String = ""                 # Display name
 @export var starts_unlocked: bool = true      # Visible at game start
 @export var purchase_currency: Currency       # What to spend
-@export var unlock_goal: GoalData             # Goal to unlock this
+@export var unlock_goal: GoalData             # Goal to unlock this (behavior defined in GoalData)
 
 # Cost formula: cost = base * coefficient^owned
 @export var initial_cost: float = 10.0        # Base cost
@@ -90,7 +90,7 @@ Runtime node instance attached to generator scenes.
 signal purchase_completed(amount, total_owned, total_purchased, total_cost)
 signal production_tick(amount, cycle_count, total_owned)
 signal buff_purchased(buff_id, new_level, cost, cost_currency_id)
-signal goal_achieved(generator_id, goal_id)
+signal goal_achieved(generator_id, goal_id)  # Emitted when generator unlocks from goal
 ```
 
 ### Key Methods
@@ -102,6 +102,10 @@ func buy_max() -> int
 func get_cost_for_amount(amount: int) -> BigNumber
 func can_buy(amount: int) -> bool
 
+# Goal-based unlock (automatic when goal completes)
+# Generator listens to GameState.goal_completed signal
+```
+
 # Production
 func grant_currency(amount: BigNumber)
 func get_effective_auto_run_multiplier() -> float
@@ -184,6 +188,22 @@ UI component showing generator information.
 - `production_tick` - Update production display
 - `generator_buff_level_changed` - Refresh buff rows
 
+## Goal-Based Unlock
+
+Generators with `unlock_goal` automatically listen to `GameState.goal_completed` signal:
+- When goal completes, generator unlocks automatically
+- Goal's `unlock_behavior` (AUTOMATIC/MANUAL) controls when goal completes
+- Manual goals require player to click "Unlock" button first
+
+```gdscript
+# In CurrencyGenerator._ready():
+GameState.goal_completed.connect(_on_goal_completed)
+
+func _on_goal_completed(goal_id: StringName) -> void:
+	if data.has_unlock_goal() and data.get_unlock_goal_id() == goal_id:
+		unlock_generator()
+```
+
 ## Prestige Integration
 
 Generators automatically apply prestige multipliers: